The purpose of this Program Project is to bring together several qualified investigators to study growth-regulated gene expression during the G1 period. The area of investigation lies between the activation of early growth-regulated genes (of which c-myc and c-fos are the prototypes) and the onset of cellular DNA synthesis. Although different cell types and different mitogenic stimuli will be used, the basic question deals with the events occurring during the G1 period and their role in activating the genes of the DNA synthesizing machinery. These studies will involve investigators from different departments who have already been collaborating closely with each other.